项目开发用到数据请求时候，会用的到`HttpWebRequest`的请求方式，主要涵盖GET、POST、PUT、DELETE等方法

一、HttpWebRequest简介

HttpWebRequest是.NET Framework中用于发送HTTP请求的核心类，适用于构建HTTP客户端。它支持GET、POST、PUT、DELETE等HTTP方法，但代码相对底层，需要手动处理请求和响应的生命周期。在.NET Core及后续版本中，推荐使用HttpClient替代，但本文重点讲解HttpWebRequest。

二、常用请求方式

1. GET请求（获取资源）

用途：从服务器获取数据（如查询API）。

步骤：

创建HttpWebRequest实例。
设置Method为GET。
发送请求并获取响应。
读取响应内容。

示例代码：

using System;
using System.IO;
using System.Net;public class HttpGetExample
{public static void Main(){string url = "https://api.example.com/data";try{// 1. 创建请求HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);request.Method = "GET";// 2. 发送请求并获取响应using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()){// 3. 读取响应内容using (Stream responseStream = response.GetResponseStream())using (StreamReader reader = new StreamReader(responseStream)){string result = reader.ReadToEnd();Console.WriteLine("Response: " + result);}}}catch (WebException ex){// 异常处理HandleWebException(ex);}}
}

2. POST请求（提交数据）

用途：向服务器提交数据（如表单提交、创建资源）。

步骤：

创建请求并设置Method为POST。
设置请求头（如Content-Type）。
写入请求体数据。
发送请求并处理响应。

示例代码：

public class HttpPostExample
{public static void Main(){string url = "https://api.example.com/submit";string postData = "username=John&password=123456"; // 表单数据try{// 1. 创建请求HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);request.Method = "POST";request.ContentType = "application/x-www-form-urlencoded"; // 设置内容类型// 2. 写入请求体using (Stream requestStream = request.GetRequestStream())using (StreamWriter writer = new StreamWriter(requestStream)){writer.Write(postData);}// 3. 发送请求并处理响应using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())using (StreamReader reader = new StreamReader(response.GetResponseStream())){string result = reader.ReadToEnd();Console.WriteLine("Response: " + result);}}catch (WebException ex){HandleWebException(ex);}}
}

3. PUT请求（更新资源）

用途：更新服务器上的现有资源（类似POST但用于更新）。

步骤：

设置Method为PUT。
写入请求体（如JSON或表单数据）。

示例代码：

public class HttpPutExample
{public static void Main(){string url = "https://api.example.com/update/123";string jsonBody = "{\"name\": \"New Name\"}";try{HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);request.Method = "PUT";request.ContentType = "application/json";using (Stream requestStream = request.GetRequestStream())using (StreamWriter writer = new StreamWriter(requestStream)){writer.Write(jsonBody);}using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()){Console.WriteLine($"Status Code: {response.StatusCode}");}}catch (WebException ex){HandleWebException(ex);}}
}

4. DELETE请求（删除资源）

用途：删除服务器上的资源。

步骤：

设置Method为DELETE。
通常不需要请求体，但可以添加查询参数。

示例代码：

public class HttpDeleteExample
{public static void Main(){string url = "https://api.example.com/delete/456";try{HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);request.Method = "DELETE";using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()){Console.WriteLine($"Status Code: {response.StatusCode}");}}catch (WebException ex){HandleWebException(ex);}}
}

三、其他常见配置

1. 设置超时

request.Timeout = 5000; // 5秒超时
request.ReadWriteTimeout = 5000; // 读写超时

2. 处理Cookie

// 获取响应中的Cookie
CookieContainer cookieContainer = new CookieContainer();
request.CookieContainer = cookieContainer;// 或者从响应头提取Cookie
foreach (Cookie cookie in response.Cookies)
{Console.WriteLine($"Cookie: {cookie.Name} = {cookie.Value}");
}

3. 设置代理

request.Proxy = new WebProxy("http://proxy.example.com:8080");

4. 处理SSL证书问题（测试环境使用）

ServicePointManager.ServerCertificateValidationCallback +=(sender, certificate, chain, sslPolicyErrors) => true;

四、异步请求

HttpWebRequest支持异步操作，避免阻塞主线程：

public async Task MakeAsyncRequest()
{HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://api.example.com");request.Method = "GET";using (HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync())using (Stream stream = response.GetResponseStream())using (StreamReader reader = new StreamReader(stream)){string result = await reader.ReadToEndAsync();Console.WriteLine(result);}
}

五、错误处理与异常管理

HttpWebRequest通过WebException抛出异常：

private static void HandleWebException(WebException ex)
{if (ex.Response != null){using (HttpWebResponse errorResponse = (HttpWebResponse)ex.Response){Console.WriteLine($"Error Status Code: {errorResponse.StatusCode}");using (Stream stream = errorResponse.GetResponseStream())using (StreamReader reader = new StreamReader(stream)){Console.WriteLine("Error Response: " + reader.ReadToEnd());}}}else{Console.WriteLine($"Network Error: {ex.Message}");}
}